This invention relates generally to slide gate valve mechanisms for controlling the flow of molten metal and more particularly to a gate safety arrangement which permits loading a gate into such a valve mechanism only when the gate has a predetermined orientation.
Valve mechanisms for controlling the flow of molten metal from a holding vessel are commonly available. One type of such valve mechanism uses slide gates which are first moved into a loaded position in the mechanism along a loading path and then moved into operative position in the mechanism along a firing path by a firing cylinder. These are commonly known as sequential type valve mechanisms. One configuration of these sequential type valve mechanisms both loads and fires the slide gates along a common path. Examples of this valve mechanism configuration are illustrated in:
______________________________________ U.S. Pat. No. Inventor Issue Date ______________________________________ Re. 27,237 J. T. Shapland November 23, 1971 3,436,023 A. Thalmann April 1, 1969 3,454,201 P. C. McShane April 1, l969 3,866,806 E. P. Shapland February 18, l975 ______________________________________
Another configuration of such sequential type valve mechanisms loads the slide gates along a loading path and then fires the slide gate into position along the firing path, perpendicular to the loading path. Example of this valve mechanism configuration are disclosed in:
______________________________________ U.S. Pat. No. Inventor Issue Date ______________________________________ 4,415,103 E. P. Shapland, et al. November 15, l983 4,545,512 E. P. Shapland, et al. October 8, 1985 ______________________________________
This latter configuration typically uses a running gate with the hole, through which the molten metal flows, offset from the center of the gate. The offsetting of the hole facilitates throttling molten metal flow through the valve mechanism by moving the running gate laterally of the firing axis. The metal flow hole through the shroud plate in this configuration is typically centered on the metal flow hole through the top plate during operation. Both the running gate and shroud gate are typically rectilinear with a slightly greater length in one direction than in the other. Thus, these gates can be reversed as they are loaded into the valve mechanism.
The fact that the running gate can be reversed has posed problems over the years since inadvertently reversing the running gate has immediate and disastrous results. This is because the valve mechanism is typically set to a closed position during gate change and reversing the running gate installs the new gate in an almost fully open position. Further, a reversed gate causes the valve mechanism to operate backwards. That is, when the running gate is reversed, the normal fully open position is the fully closed position and the normal fully closed position is the fully open position. In addition, a reversed running gate prevents making any gas connections normally made directly to the running gate so that the molten metal being poured is typically downgraded to a less desirable grade of steel.
A reversed shroud gate may prevent making those gas connections normally made directly to the shroud gate or tubular shroud and cause a downgrading of the molten metal being poured.